Significant prognostic difference between Grade Group 4 and 5 in the 2014 International Society of Urological Pathology Grading System for High Grade Prostate Cancer with Bone Metastasis

Background: To investigate prognostic difference between Gleason Score (GS) 8 and 9–10, as the 2014 International Society of Urological Pathology Gleason Grading Systems proposed, in patients with prostate cancer (PCa) with bone metastasis. Materials and methods: We retrospectively reviewed data on 106 patients with GS 8–10 between 2006 and 2016. All patients received androgen deprivation therapy immediately. We validated biochemical recurrence, PCa-specific survival, and overall survival, and analyzed the predictive value for overall survival. Results: Patients with GS 9–10 had significantly lower PCa-specific survival (50.5% vs. 83.4%, P=0.01) and overall survival (38.8% vs. 66.3%, P=0.04) at 5 years than those with GS 8, while biochemical recurrence rate was not significantly different (P=0.26). Furthermore, these significant differences between GS 8 and 9–10 were also observed among high-risk groups proposed in Japan Cancer of the Prostate Risk Assessment Stratification (prostate cancer-specific survival: P=0.03, overall survival: P=0.04, respectively). Pathological GS 9–10 was an independent prognostic factor for overall survival (hazard ratio=1.97, P=0.04) in multivariable cox proportional hazard regression analysis. Among patients with GS 9–10, albumin level was an only prognostic factor for overall survival (hazard ratio=0.33, P